The knee is generally regarded as being the most inherently unstable of the joints of the human body, due in part to the complex inter-related types of motions to which the several knee elements are subjected during ambulatory movements of the body. Various prostheses have hithertofore been proposed in attempts to approximate, through an artificial joint, the natural action of the human knee. Advanced conditions of disease or serious traumatic injury of the knee joint complicate surgical repair and efforts to simulate the natural knee motion through use of a prosthesis.
Several types of prostheses, each having advantages and disadvantages have been employed. One type currently in use is the hinged type such as described in my U.S. Pat. No. 4,262,368. Other prostheses are employed in which the femoral and tibial components are unconnected. Most of the latter systems rely on the use of bone cement to assist in anchoring the prosthesis to the resected femur.
U.S. Pat. No. 4,355,429 discloses a knee joint prosthesis which is secured without cement. Anchoring is accomplished by utilizing pins inserted into slightly undersize holes drilled into the bone. There is no disclosure of the use of dual T-shaped fins or flanges integral with the implant which serves to stably, mechanically anchor the device.
U.S. Pat. No. 4,217,666 discloses a tibial prosthesis component which uses an intermedullary stem of U-shaped configuration in order to retain the cruciate ligament. It is further stated that the stem may be texturized with grooves, perforations or ridges. The prosthesis is, however, disclosed as being implanted with the aid of bone cement.
The general objects of the present invention are to provide an improved tibial prothesis designed for insertion without cement. The implants of the present invention provide immediate mechanical fixation to the bone by the use of a combination of an intermedullary anchoring stem and medial-lateral fin type elements having intersecting fin type elements at each end which are designed to be implanted in a resected tibia into which slightly undersized apertures or slots have been osteotomized. The fins create a dual T-pattern that resists torsional forces. Such configuration and placement of the fins has been found to provide stable anchoring of the prosthesis wihout the use of bone cement.